How Australia's fight against 'jarrah dieback' could help NZ save kauri

An Australian forest pathologist says there are plenty of things New Zealand can learn from his country's experience with dieback disease, as we try to save our kauri.

A similar pathogen to kauri dieback has been laying waste to Australia's native plants since the 1960s. It used to be called 'jarrah dieback', as it killed the native jarrah trees.

But Professor Giles Hardy, from Murdoch University in Perth, says this name is no longer an accurate descriptor.

"People started to notice that many other plant species in heathlands and woodlands were dying, not just jarrah," he tells Newshub Nation.

"Subsequently we've discovered that jarrah are actually quite resistant to the pathogen but many others species are very susceptible."

How Australia's fight against 'jarrah dieback' could help NZ save kauri
Photo credit: Gaia Resources, Enviromental Energy Consultants

There are just under 7000 plant species in South West Australia and 41 percent are susceptible to the dieback pathogen.

"So there's been very substantial devastation," says Prof Hardy.

Cross-species contamination is a concern with kauri dieback - and lab tests show it's already happening.

"We know already that it infects rewarewa [and] tānekaha, and that it hides cryptically without causing symptoms in pine forest and pasture," the Tree Council's Mels Barton tells Newshub Nation.

Both types of dieback are caused by phytophthora, a microscopic type of mould. Phytophthora agathidicida is the scientific name for kauri dieback, while the Australian type is called phytophthora cinnamomi.

How Australia's fight against 'jarrah dieback' could help NZ save kauri
Photo credit: Newshub Nation.

Soil is the main way both pathogens are spread. When it gets wet, the spores germinate and are able to swim through the soil looking for roots. They then infect the plant's tissue, stopping water and nutrients from reaching the canopy - eventually killing their host.

Prof Hardy says there were a couple of things Australia could have done better.

"Making sure you have really good collaboration between the agencies, universities and key stakeholders… that social buy-in is really important," he says.

"The other one is implementing really uniform signage. For a while there was different signage being used to try and educate or inform people, so tourists and others moving through the landscape were getting different messages and that was confusing."

He also stresses the importance of accurate and up-to-date mapping of infected areas, as well as quarantine measures for some healthy forests.

"We've selected these priority sites that can be protected and quarantined for the next 50 to 100 years."

The quarantine measures include no-go zones, security cameras and vehicle and footwear cleaning stations, as well as the rerouting of roads and walking tracks away from infected or protected forests.

The use of the chemical phosphite has been proven to help plants fight dieback in both Australia and New Zealand.

"We use it on sites where we have rare or endangered plant species that are highly susceptible, and would disappear off the planet if we don't use phosphite," Prof Hardy says.

In jarrah and kauri, the chemical is injected into the trunk and helps the trees keep the pathogen at bay by boosting their immune systems.

Phosphate injections on a kauri tree.
Phosphate injections on a kauri tree. Photo credit: Horner/MPI

But while injections work well as an individual fix, it's harder to use as large-scale treatment.

"We do apply [phosphite] in Australia from fixed-wing aircraft as a mist over strategic areas that we want to protect, especially on rare or threatened plant communities," Prof Hardy says.

However he says phosphite is only a temporary solution for the short- to medium-term, while better control methods are developed for the long-term.

Eradication of dieback has been successfully trialled in Australia in small areas by making an area fallow or barren for a few years.

"The pathogens need to have a living host in order to [survive and reproduce], so they die quite quickly," says Prof Hardy.

"Within two years of fallowing we can actually start to rehabilitate, so this is something we're looking at more and more."

But eradication would be much more difficult in New Zealand forests due to the difference in terrain, Prof Hardy believes.

"It could probably be used if they were wanting to plant kauri on ex-farm sites or cleared sites where the pathogen is present," he says.

"Prior to planting they could go through the fallowing process and once they've eradicated the pathogen, plant back then onto those sites and maintain very strict hygiene.

"So there would be situations, but I think it would be very challenging."

Newshub Nation.

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